Cultivation of human embryonic lung (HEL) cells in media containing acetylsalicylic acid (ASA) at 100 pg/ml and maintenance at this level after inoculation with either cell-free varicella zoster virus (VZV) or virus-infected cells resulted in a 2-to 4-fold increase in yields of cell-free virus released by sonication. The degree of enhancement was dependent upon multiplicity of infection and time of harvest. Enhanced viral yields were not consistently accompanied by an increase in the number of infected cells, nor was VZV plaque formation in HEL indicator cells significantly increased in the presence of ASA at 100 pg/ml. In the presence of ASA at 500-1000 pug/ml, VZV plaque formation was inhibited; this inhibition was partially reversible, depending on concentration and period of exposure to ASA. These findings may bear on the apparent association between ASA ingestion and the development of Reye syndrome after infection with varicella virus. METHODS AND MATERIALSTissue Culture and Virus. Two lines of human embryonic lung (HEL) fibroblast cultures were prepared and maintained on Eagle's minimal essential medium supplemented with 2% fetal calf serum, penicillin at 100 units/ml, streptomycin at 100 ,ug/ml, or gentamicin at 100 ,ug/ml. One line was used in the 4th to the 10th passage and the other in the 22nd to the 39th passage. The strain of VZV was isolated from a patient with varicella and used after 19-55 cultural passages. Stock virus was prepared and cell-free virus was concentrated with polyethylene glycol 6000 as previously described (7).Harvest of Virus. Virus-infected cells were harvested by washing infected cultures maintained in 25-cm2 Corning flasks with phosphate-buffered saline and incubating for 5-10 min with 1.0 ml of 0.25% trypsin in phosphate-buffered saline at 370C; the detached cells were then transferred to 10% fetal calf serum in phosphate-buffered saline to inactivate residual trypsin, centrifuged at 180 x g for 10 min, resuspended in 1.0 ml of Eagle's minimal essential medium, and kept at 40C. Cell-free virus was obtained from three cultural sources: (i) Growth medium. Five milliliters of growth medium was removed from infected cultures maintained in 25-cm2 flasks and centrifuged at 400 x g for 15 min, and the supernatant was kept at 40C. (ii) Glass bead treatment. Infected cells were harvested mechanically by addition of 10-15 glass beads (2-3 mm in diameter) and 0.5 ml of SPGA medium (8) to each flask; after gentle shaking the freed cells were removed and the flask was rinsed twice with 0.5 ml of SPGA; the cells and washings were centrifuged at 600 x g for 15 min, and the supernatant containing virus was kept at 40C.(iii) Sonicated infected cells. The cellular sediment after centrifugation was resuspended in 1.0 ml of SPGA, sonicated in a 40-ml conical centrifuge tube with the microtip of a model W 200 Heat Systems sonicator (60% power, 10-15 sec), and centrifuged at 600 x g for 15 min, and the supernatant fluid was kept at 4°C. The total amount of cell-free virus mechanically re...

Guinea pigs were inoculated by the respiratory route with wild-type (Cyr) or vaccine (Oka) strain varicella zoster virus (VZV). Wild-type cell-free virus obtained by sonication produced neutralizing antibody responses in steroid-treated animals when given via the intratracheal route, and induced neutralizing antibody as well as a pneumonitis in normal animals when given via the intrabronchial (i.b.) route. A humoral response also followed i.b. instillation of cell-associated wild-type or vaccine strain VZV. Prior i.b. administration of thioglycollate or exposure to hyperoxia altered the number and function of pulmonary macrophages, respectively, but viral susceptibility of the guinea pigs was not enhanced. Both strains of VZV could be isolated from bronchial washings up to 48 hours after i.b. instillation of cell-associated virus, but neither strain was isolated thereafter from cultures of bronchial washings or explanted lung tissues.